Japanese sokuon, or geminate consonant, is claimed to affect the duration of the adjacent vowels on both sides. Previous studies have found that vowels are longer before sokuon and they are shorter after sokuon. The speech materials used in these studies are read-aloud phrases or short sentences. In order to evaluate if these findings hold true in spontaneous speech, we analyzed the Corpus of Spontaneous Japanese. The results revealed that vowels as well as mora nasals are longer before sokuon. However, no clear tendencies appeared for the duration of vowels after sokuon. The effect of sokuon on the preceding vowel is robust in both stop consonants and in fricatives. Articulatory correlations with the vowel duration are discussed.
To clarify accent variation in natural speech, this paper investigated the distributional pattern of the occurrence of compound accents (CA) using a Japanese Accent Dictionary (JAD) and the Corpus of Spontaneous Japanese (CSJ). Japanese is known to have CA assignment rules: in the case of noun-noun compounds, CA is assigned systematically according to the characteristics of the element nouns. Essential results obtained from JAD and CSJ analyses of CA show that the co-occurrence of unaccented pattern and antepenultimate accent is found in both JAD and CSJ. This variability might be brought about by a language shift in rule level, a higher level of the Japanese phonological system, rather than to individual lexical level.
Previous studies on sokuon, or Japanese geminate consonants, have mainly focused on the acoustic properties. Some studies claim that laryngeal characteristics also differ between sokuon and singletons. However, physiological studies on sokuon are not well explored. This study uses a high-speed digital video system and PGG to examine whether any laryngeal/glottal tension takes place in producing sokuon. The results showed that no apparent laryngeal constriction or glottal stop appeared during sokuon. However, the analysis of PGG and kymograph showed that the glottal opening tends to be suppressed during sokuon during the onset part, suggesting that some kind of tension of the vocal folds is involved in producing the phoneme.
The place of articulation in Japanese moraic-nasals is known to vary in accordance with the following sound and is assumed to be uvular in the word final position. This paper attempted to describe articulatory variability of word-final moraic-nasals using the X-ray microbeam speech production database in Japanese. The results depicted substantive inter-speaker variability in three of the four words examined. Moreover, 75% of the data examined were deemed unlikely to be uvular nasals and the lips were likely to be closed in 40% of the data. The results do not support the claim that word-final moraic-nasals are uvular.